Evaluation of shear bond strength of repair acrylic resin to Co-Cr alloy

Purpose: The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr. Materials and methods: Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with Al2O3; Co: airborne particle abrasion with silica-coated Al2O3; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison' test performed uing a post hoc Tukey HSD test (?=.05). Results: Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001). Conclusion: Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano- Pen did not cause a significant reduction in adhesion after thermocycling. © 2014 The Korean Academy of Prosthodontics

Evaluation of zirconia and zirconia‐reinforced glass ceramic systems fabricated for minimal invasive preparations using a novel standardization method

Objective: Currently, minimal invasive approaches combining less invasive finish line preparations and reduced ceramic thickness are required. The aim of this study was to evaluate the fracture resistance of two ceramic systems fabricated with two preparation designs using CAD/CAM standardization technology. Materials and methods: Forty intact human maxillary premolars were divided into two main groups according to the preparation technique. Group H (Horizontal): teeth with shoulder finish line and group V (Vertical): teeth with feather edge. Each main group was subdivided randomly into two subgroups according to the material used. Group CD (Celtra Duo) zirconia-reinforced glass ceramics and group K (KATANA) monolithic zirconia. CAD/CAM was used for standardization of natural teeth preparation. After cementation using self-adhesive resin cement, all specimens were subjected to 5000 thermal cycles and then were loaded until fracture. Failure types were evaluated using Stereomicroscopy and Scanning Electron Microscopy (SEM). Results: Nonsignificant; the higher mean value was recorded with VCD group (482.5 ± 103.8 N) and VK group (1347.6 ± 177.4 N) vs HCD group (471 ± 107.6 N) and HK group (1255.6 ± 121.3 N). SEM findings showed that fractures occurred mainly at the occlusal side of the crowns. Conclusions: Vertical preparation showed a promising alternative to horizontal preparation. Moreover, both Celtra Duo and KATANA crowns can be used in premolar area with 0.5 mm margin thickness. Clinical significance: Zirconia-reinforced glass ceramic and monolithic zirconia crowns may not necessitate the preparation of invasive finish lines as the type of finish line did not impair the strength after aging condition

The effects of trade wars between us and china on the financial performances of the companies

Tariffs that the USA has implemented in some products toward China have recently caused trade wars. Trump, who was elected US president in 2016, triggered trade wars due to his protectionist attitude towards China. That’s why trade wars officially started in 2018. This attitude of Trump influenced also the stock exchanges of the two countries as well as the trade relations of the two major economies. While our study provides information about the US-China trade wars, it empirically tested the relationship of this war with the stock markets of both countries. The relationship between exports made mutually by the USA and China and the stock exchange is analyzed using the Engle-Granger cointegration method. In this study, which was used monthly data for the period 2016–2019, a long-term relationship between exports and stock market is detected for both countries. Considering the global economy within the framework of this relationship, it is seen important that the two countries withdraw commercial wars and go for an agreement